Method and apparatus for treating oils



Jam.` 17, 1933. w. G. LAIRD METHOD ND APPARATUS FOR TREATING OILS 2 Sheets-Sheet 1 Filed July 50, 1926 Jan. 17, 1933. w. G. LAIRD 1,894,355

METHOD AND PPARATUS FOR TREATING OILS Filed Jul-yO, 1926 2 Sheets-Sheet 2 ff W/LBUK 6. LAIRD /f/'S @Mor/mm3 i cause the residuum Patented J. 17, 1933 sTATES PATENT OFFICE a e. i or or .N Yoan, N. Y., A

@D .AND APPARATUS FOB- TREATLNG OILS Application med July 30,

'lhis invention relates to an' improved method of and apparatus for the distillation or cracking of petroleum oils for the production of gasoline and other commercial products therefrom.

More particularly the invention relates to the treatment of residuum and reflux condensate produced in pressure cracking systems, in which highly heated oil from a heater is discharged into an enlarged reaction chamber to complete the cracking operation and to eect the separation of vapors from residuum.

ln previous pressure processes for cracking petroleum oils charging stock has been passed in heat interchange relation to the vapors in' a dephlegmator, the redux condensate from the vapors then being added to this stock and the mixture passed to the heat- `ing coil. Also the unvaporized or residue oil has been removed from the reaction chamber and added to the charging stock or distilled by releasing the pressure., lin these processes part of the gasoline which has already been produced in the cracking zone and which is absorbed or occluded in the redux or residuum is again returned to the cracking Zone where it may undergoY decomposition or is lost in the discharged residuum. Considerabledifculty has been exerienced in the transfer of the highly beate residuum through valves and conduits and release of the pressure beis considerably above its dashing temperature vvhen the pressure is released for evaporation- An object of the present invention is to provide a method and apparatus which will overcome the objectional features mentioned above and also increase the yield of gasoline from a given quantity of charging stock.

The present invention comprises a combination of important steps by which the emciency of the cracking operation is materially increased. When any product such as the residuum is-.fwithdravvn from a cracking system it contains a rather definite percentage of occluded and absorbed gasoline. lf this residuum is returned to the cracking still as in some processes, the gasoline present there- 50 in will prevent thev formation of an equal 1926. Serial No. 1255893 amount of gasoline from the cracking stock `due to the equilibrium conditions which are established. lBy my novel process any prode ucts withdrawn from the cracking system, such as residuum and reflux condensate and which are to be recirculatcd through the cracking still for retreatment are lirst stripped or topped of their gasoline content. Thus assuming that the initial charging stock is a gas oil, the topped residuum and reflux condensate mixed with it and passed to the cracking still gives a nal charging stock which is dry with respect to gasoline (except Where the initial gas oil is used as an absorbing medium in the manner referredto hereinafter) and therefore the conditions are such as to favor the maximum yield of gaseline in the cracking operation. It is evident that by this procedure l obtain a two-fold ciciency in my gasoline ordinarily left in the redux and the residuum is recovered and the yield of 'gasoline is increased by having the cracking stock free of gasoline. lin effecting the topping of the residuum and redux l maintain these ma terials under the pressurev of the cracking sys tem and also maintain or even increase their temperature, whereby I am able to discharge the topped vapors directly intothe vapors from the cracking still and at the same time pass the topped products back to the cracliu ing still with a minimum utilization of power and loss of heat. instead of returning residea uurn to the cracking still l may strip in the manner referred to above except that in this case it is also stripped of all fractions lighter than the fuel oil residue.. These frac tions which will include the gas oil.a kerosene and similar fractions are introduced in vapor form directly into the highly heated oil and vapors passing to the reaction chamber from the cracking still, Which will result in theA cracking of these fractions. f

Other objects and advantages will appear from the following detailed description taken in connection with the accompanying draw ings, forming part of this specicatione Referring to the drawings,

Fig. 1 is a diagrammatic view in elevation of an apparatus in which the preferred met/hrVv cracking system, since the od of the present invention may be carried on g Figs. 2 and 3 are enlarged views in elevation at rightangles to each other, of the column shown in Figure 1, Fig. 2 being taken looking from the left of Fig. 3 and Fig. 3 taken looking from the right of Fig. 2, certain parts are broken away to show inside structural features.

The oill to be treated which may be either crude or stripped petroleum or a distillate thereof, first enters the system through feed line 2, which discharges into the top of absorber 4. In the absorber the oil passes counter to rising non-condensed gases from vthe system which enter the absorber through conduit 6. Oil is withdrawn from the absorber, where it has taken up 4any gasoline vapors in the gases, through conduit 8 by pump 10 and deliveredthrough line 12 under pressure to the first of a series of heat interchangers 14, in a fractionating column or dephlegmator 16.`

Gas from the absorber ismiXed` with feed oil inthe line 12 by compressor 18 and interconnecting pipe llnes 20 and 22, excess gas from the absorber being removed by valved pipe 24.

The feed stream now consisting of a mixture of oil and gas is fed through the series of heat interchangers 14'in the column as indicated by the arrows on dotted line 26 run- 'ning through the interchangers, finally leaving the tower through the lowermost interchanger by conduit 28, Fig. 1. The conduit 28 conducts the feed stream to heating coil 30, mounted in heater 32 where the oil is heated to the desired distilling or cracking temperature by burner 34. Heated oil from the coil 30 which may be at a temperature of .from 775 to 950 F. is conducted by pipe 36 tothe inclined reaction chamber 38, where vapors are ermitted to separate from unvaporized oil and residuum. Vapors leave the reaction chamber by vapor line 40 and enter the lower portion of the tower 16 where they pass in countercurrent relation to the charglng oil through the interchangers 14 as indicated diagrammatically by the arrows on dotted-V line 42. The vapors leaving the tower are rectified gasoline vapors and are passed by Vapor offtake 44 to condenser 46,

the condensate and non-condensed gasesv being separated in trap 48. The gasoline product is withdrawn by valved pipe 50 While the gases pass to the absorber by pipe 6, previously referred to.

The reaction chamber 38 referred to above may be of any approved type, but is shown as comprised of an inclined chamber having a series' of transverse baille plates 52, below which the vapors must low, liquid being preferably maintained in the chamber so as to cover the upper side of the plates t9 a certain extent. It is evident that the vapors -"passing under the plates will maintain the `The residuum 'containing the carbon and sludge is withdrawn from the lower part of the reaction chamber by valved conduit 54 into a stripping chamber 56 set in masonry heating chamber or furnace 58, while the relatively clean residuum is withdrawn from the upper part of the chamber 38 by valved conduit 60 into topping' chamber 62. The residuum withdrawn from the lower part of the chamber 38 may be forced into chamber 56 by closing the valve in line 54 and utilizing a by-pass line 53 which includes a pump 55. lln a similar manner the oil withdrawn through line 60 may be forced into chamber 62 by the use ofa by-pass line 59 into which is linserted a pump 61.

rlhe stripper 56 is' provided-with a gas distributor 64, which is supplied with gas from any suitable source. The gas iiows through a-heat interchanger 66, pipe 68 and fheating coil 70' so that it is preheated when it reaches the distributor -641 Vapors from the stripper maybe passedl direct to transfer line 36 by pipe 7201' to the upper end of reaction chamber 38 by pipe 74 or to the dephlegmator 16 by line 76. Valves are pro-` vided in these lines for'directing the iow as desired. The stripped residuum is withdrawn from the stripper` 56, through interchanger 66, where' it preheats the gas, then through cooler 78 and is finally discharged through valved pipe 8() to be used as fuel oil.

The topper 62 is 'a baiiied chamber provided with a gas distributor 82 supplied with gas from any suitable source through plpe 84. Vapors from chamber 62 may be passedby pipe 86 to lthe lower end of the reaction chamber, direct to vapor line 40 by pipe 88 or to the lower end of the dephlegmator by pipe 90. The topped residual oil from chamber 62 is withdrawnthrough conduit 92 by pump 94, and passed throughn conduit 96, having valved branches 98, directly into the 'charging line at any desired point in the column 16 or directly into ,the feed line 28 by valved pipe 99. As previously mentioned it may be desirable in certain cases not to recirculate the residuum back through the cracking still. ln which case the topping still 62 is cut out Aof the system and the whole of the residuum from the reaction chamber is withdrawn into the still 56, which may be operated in the manner previously. explained, but .is preferl ably operated at a tem rature such that the vapors and gases there rom may be delivered directly into the transfer line 36 without causing any substantial reduction in temperature therein. By this method of treating the residuum the chargin stock is passed through the cracking still but once and the gas oil and other higher volatiles stripped from the residuum are cracked in vapor phase by being mingled in line 36 with the hot oil and vapors coming from the crackingstill. In order to prevent deposition of carbon in the reaction chamber I maintain the oil in the reaction chamber at afairly low specic gravity and by passing a relatively large amount through the stripper 56 from which the fuel oil containing the carbon from the cracking operation is removed.`

ln the column 16 below the vapor line 40 are positioned'a series of bae plates 100 and a gasdistributor 102 which is supplied with gas from a valved conduit 104 or by gas and vapor by conduits 7 6 and 90 which discharge into the conduit 104. Reflux condensate accumulating in the lower part of the column is topped of occluded and absorbed gasoline vapors by the gas or gas and vapor from the distributor. The topped redux is withdrawn by pump 106, in conduit 108 and passed at any desired point into the charging stock flowing downward through the column, by branch pipes 110. y

ri`he construction of the column is shown umore particularly in Figs. 2 and 3. The

charging stock enters the first of the series of interchangers 14 by the conduit 12, and passes from unit to unit by the conduits 112 finally leaving the last of the series by the conduit 28. The interchangers 14 are'all constructed alike, each comprises an elongated cylinder having'clsed ends with tube sheets 114 spaced therefrom. Between the tube sheets are mounted a group of tubes 116 as in the common surface condenser. The charging stock enters each unit 14 between the tube sheets near-the tube sheet in one end and flows around the tubes, leaving the unit near the opposite tube sheet. The vapors passing through the units 14 enter the space- 118 at one end between the tube sheet and the end plate by conduit 120, pass through the tubes 116 to enter' the opposite space 118 from which they pass into the column proper by conduit 122.

The heat interchanger units 14 are mounted crosswise of the column 16 and are constructed integral with it in order to provide for uniform expansion and contraction. At each unit 14 in the lower part of the vcolumn is a. dead plate 124 extending across the column to direct the vapors into conduits 120. Between adjacent dead plates are bubble plates 126, of the ordinary type having bubble caps 128. The vapors after passing through a unit 14 pass by conduit 122 below `through t the next bubble plate and under the bubble caps through condensate maintained upon the bubble plates. Reflux condensate on the bubble plates overflows into pipes 130 discharging ont-o the next bubble plate below and from the lowest bubble plate into overow pipe 132 which discharges into a liquld seal 134 in the lower part of the column. rl`his seal is used to guard against the liquid level falling below pipe 132. Any condensate formed or accumulating on the dead plates or in the units 14 flows counter to the vapors throu h conduits 122, tubes 116 and conduits 120,ack onto the next bubble plate below.

In the upper part of the column the vapors are passed directly from interchanger to in terchanger by the conduits 136 without being passed through bubble plates, and the condensate formed in the upper four interchangers 14 may bedirected to flow out with the vapors into condenser 46.

Avery material advantage is obtained 1n the erection of the tower by constructing it in sections, each comprising one or two interchanger units which may be assembled at the place where it is to be used.

In carrying out the novel method the residuum containing the carbon and sludge may be withdrawn from the lower end of the repors driven oil' are passed directly into the .transfer line 36 unless they are cooler than the liquid in the reaction chamber, in which case they are delivered by the vapor lne 74 into the upper end of the reaction chamber. It is desirable to strip the residuum of all absorbed or occluded gasoline vapors as well as any oil that would be suitable' for recycling through the heater. This will leave the strip ed residuum to be discharged iie conduit 80 to any desired point of consumption as fuel oil.

If the residuum is withdrawn intermittentY ly and treated in batches in the stripper 56, the light volatiles such as asoline vapors together withthe gas intro uced through dis- 102 by conduits 76 and 104 and used alone or in conjunction with other gas to strip the i reflux condensate collecting inthe bottom of the column. After the light volatiles have been removed from the charge in the stripper the remaining vapors are discharged through lines 72 or 74 as when running continuously. The pressure of or above that maintained on the reaction chamber is maintained on chambers 56 and 62 as will be apparent from the fact that the vapors from these chambers' are mingled with those from the heater. Any pressure may be maintained on the system rom atmospheric ,to upward of several hundred pounds per square inch as may be desirable.

`When operating the heated stripper 56 by either the continuous or the vintermittent method the whole of the vapors driven. off may be passed by vapor lines 7 G and 104 into the lower end of the column 16 where they mingle with the cooler reflux condensate. By this procedure a direct mixture of the gas oil, kerosene or other fractions removed from the residuum is obtained with the reflux condensate. This mixture after being topped of gasoline is withdrawn from the column by pump 106 and passed to the cracking st ill.

In topping the relatively clean residuum withdrawn from the upper end of the reaction chamber by the conduit 60 into baffled chamber 62, gas, which may be heated is introduced through the distributor 82, passes up through the oil and removes the absorbedor occluded gasoline vapors. -If the gas is not saturated on leaving chamber 62 1t may be passed through conduits 90 and 104 into the reflux condensate in the bottom of the column or may be discharged either into the lower end of the reaction chamber or directly into the vapor line 40 by operating the appropriate valves in conduits 86, 88 and 90. If the vapors are being passed through the line 86 to the lower end of the reaction chamber it may be necessary to open the lower outlet valve in the line 60 or use the by-pass line 59 and pump 61, because the pressure difference in passing the vapor back will necessarily lower the level of the oil in chamber 62 to correspond with the pressure difference, otherwise the upper outlet valve is used. The topped oil withdrawn from topper 62 .by

ump 94 is mixed with the advancing charging stock at any desired point in the column by one of the branch pipes 98 connecting directly with the feed lines 112 between the inter-changers as shown in Figs. 2 andI 3, or if the oil is hotter than the vapors in the tower it is 'added to the charging stock in the line 28 by using the valved pipe 99. l

The topping of the reflux condensate in the column may be accomplished by using either hot or cold gas. The vapors removed mingle with the vapors entering through the vapor line 40 and pass upward Ithrough the column. The topped reflux condensate withdrawn may be introduced into any desired point in the feed stream by the branch pipes 110 which connect directly to the feed lines 112 between the interchangers 14.

`The gas used for stripping or topping in the chambers 56, 62 and the column 16 may be any suitable gas such as steam but preferably the stripped gas from the absorber 4.

In operation of the apparatus the various conduits and chambers which contain hot products are preferably covered with heat insulating material to prevent as far as possible heat 'loss due to radiation.

lt will be apparent from the foregoing description that by stripping the lighter vapors and topped reflux to the feed stream in the.

condensing column li am able to control the temperature in the column and at the same time form a cracking stock of a very desirable character. Any desired proportions of the various constituents may be used in making up the stock which is passed to the cracking zone. However, it has been found desirable when treating heavy crudes or cuts thereof, to add to it in the column a considerable quantity of a more volatile stock, which may be either the' topped reflux or topped residuum or both. f

What I claimis:

1. A method of cracking oils comprising continuously advancing oil toward a cracking zone in heat interchange rela-tionto but out of contact with vapors and gases from said zone, condensing higher boiling portions of said vapors, topping said condensate to drive off occluded and absorbed light oils and adding the topped condensate to the advancing oil while in said heat exchange with said vapors.

2. The method of cracking oils as defined in claim 1, in which the light oils removed from said condensate are mixed witl1 said vapors and gases to pass in heat interchange with said advancing oil. v p

3. A method of cracking oill comprising advancing oil under pressure through a zone heated to a cracking temperature and a separating zone where vapors are permitted to separate from residual oil, withdrawing the separated vapors, stratifying'the residual oil due from the lower stratum of residual oil, stripping the withdrawn residue of lighter fractions out of contact with said vapors, and adding said fractions to the vvapors from the heating zone. I

4. A method of cracking oil comprising advancing oil under pressure through a zone heated to a cracking temperature and a separating zone where vapors are permitted to separate from residual oil, withdrawing the separated vapors, stratifying the residual oil in the separating zone to separate ta'rry residue from relatively clean residual oil, removingv the clean separated residual oil from said separating zone, topping said removed oil out of contact with said vapors, adding thevapors formed to the vapors from the heating zone and adding the topped oil tothe oil that is to be so advanced.

5. The method of cracking oils under pressure, which comprises, passing oil under pressure through a crackin still and into a reaction chamber to comp ete the cracking claim 5 in which highly heated gas is passed through said residuum to perform said stripping.

7. The method of cracking petroleum oils which comprises passing sai 011s under pressure through a cracking zone and into an -enlarged chamber where the cracking operation is completed and the vapors formed are separated from residuum, withdrawing said residuum from said chamber, heating said withdrawn residuum to drive oil' vapors therefrom and passing. said vapors into the highly heated oil leaving said cracking zone. 8. The method of fractionating oil vapors, comprising passing vapors alternately through bodies of reflux condensate and in heat interchange relation with oil to be heated, but out of contact therewith, withdrawing reflux condensate from said bodies, topping said withdrawn reiiux condensate and mixmo` the topped product with said oil to controll the temperature of said vapors.

9. An apparatus for treating liquids comtically spaced along said column, means for passing oil to be cracked through said interchangers in succession, means for passing vapors through said interchangers but out of contact with said oil, means for topping condensate formed lin said column and means for passing said topped condensate into said oil at an intermediate point in said column.

13. In the process of cracking hydrocarbon oils in Vwhich the oil is passed under a superatmospheric pressure in a confined stream through a hea-ting zone in which'the oil is heated to a cracking temperature and from which the oil is discharged into an enlarged separating zone in which vapors are separated from the unvaporized residuum, the improvement which comprises withdrawing separated residuum from said enlarged separating zone into a separate distilling zone, re-

moving the lower boiling constituents fromv said residuum in said distilling zone, and passing the 4removed constituents into and mixing them with the highly heated o1l products passing from said heatlng zone into sa1d enlarged separating zone.

In testimony whereof I aiix my signature.

WILBUR G. LAIRD.

prising a reaction chamber, a fractionating chamber receiving vapors from the reaction chamber, a topping still receiving liquid from said reaction chamber, means for withdrawing condensate from said fractionating chamber, means for mixing topped oil from said still with said condensate and for passin said mixture in indirect heat interchange wit said vapors.

10. Inan apparatus yfor treating liquids, a fractionating column, means for advancing liquid to be treated downward through the column in4 indirect heat interchange with vapor passingupward through said column to produce a condensate therein and means for passing said condensate into said advancing liquid at an intermediate point in said column.

11. A fractionating column comprising a series of elongated horizontal heat interchangers vertically spaced along said column, means for passing ayfcooling fluid through said interchangers in succession, means for 

